1. Field of the Invention
The present invention relates to a semiconductor inspection system for inspecting defects, such as recesses in a semiconductor wafer, as well as to a method of manufacturing a semiconductor device including a step of inspecting recesses in a semiconductor wafer.
2. Background Art
If foreign particles or defects arise in a semiconductor wafer, the foreign particles or defects causes an impediment in a process of manufacturing a semiconductor device from a semiconductor wafer. Further, such foreign particles or defects exert significant influence on the characteristic of the semiconductor device manufactured from the semiconductor wafer. An inspection step of measuring the size and density of foreign particles present on a semiconductor wafer is indispensable for the process of manufacturing a semiconductor device.
FIG. 10A is a block diagram showing a configuration of a conventional semiconductor inspection system.
The conventional semiconductor inspection system shown in FIG. 10A comprises a control section 10 for storing data and controlling the overall inspection system; a console section 11 for mechanically actuating a wafer transporting device; and an inspection section 12 for inspecting foreign particles on a semiconductor wafer. FIG. 10B simultaneously shows a detailed configuration of the inspection section 12. In the drawing, reference numeral 1 designates a semiconductor wafer which is an object of inspection, and reference numeral 6 designates a foreign particle adhering to the surface of the semiconductor wafer 1. Reference numeral 2 designates a laser beam radiation section for radiating a laser beam onto the semiconductor wafer 1. The laser beam radiation section 2 can radiate a laser beam on the semiconductor wafer while scanning the semiconductor wafer. Reference numeral 3 designates a reflection section for reflecting the light scattered from the foreign particle 6; 4 designates a light converging section for converging the light reflected from the reflection section 3; and 5 designates a detection section (photo-multiplier: PTM) for detecting the thus-converged light.
On the basis of a flowchart shown in FIG. 11, procedures for inspecting an extraneous object on a semiconductor wafer through use of the conventional semiconductor inspection system will now be described.
First, a reference wafer to be used for inspecting an foreign particle as shown in FIG. 11A is prepared. The reference wafer is prepared by means of coating a wafer, which is identical in size with a semiconductor wafer to be inspected, with a plurality of foreign particles of identical size; that is, polystyrene particles (PSL). A plurality of wafers are prepared, each wafer being coated with foreign particles of a different size.
The sizes of different foreign particles provided on the reference wafers are measured, through use of the semiconductor inspection system shown in FIG. 10. The reference wafer is inspected by means of a laser beam being radiated, in a scanning manner, on the semiconductor wafer 1 from the laser beam radiation section 2. The detection (PTM) section 5 detects the intensity of the light scattered from the semiconductor wafer 1. At this time, the relationship between intensity of scattered light and the resultant count value is plotted for each reference wafer, as shown in FIG. 11B.
On the basis of the graph relating to the relationship between intensity of scattered light and the resultant count value, the graph being defined for each of the reference wafers coated with a foreign particle of a different size, the intensity of scattered light corresponding to the maximum count value is defined as the intensity of scattered light for a foreign particle of each size.
Next, a sensitivity calibration curve is prepared. As shown in FIG. 11C, the sensitivity calibration curve is prepared by means of plotting the relationship between PSL particle size and intensity of scattered light.
A real wafer which is to be actually subjected to foreign particle inspection is measured, whereby the relationship between the intensity of scattered light and the resultant count value is examined. By reference to the sensitivity calibration curve, there is performed computation of foreign particle data; that is, estimation of distribution (i.e., the sizes and locations) of foreign particles on the real wafer.
The conventional semiconductor inspection system and the conventional foreign particle inspection method have been embodied as mentioned previously.
The conventional system and method enable measurement of foreign particles which are present on a wafer surface in the form of projections. In a case where crystal-originated particles (COPs), which are crystal imperfections of a wafer, or recesses, such as micro-scratches formed during a chemical-mechanical polishing step during wafer processing, are present on a wafer, the conventional system and method encounter the following problems.
The light scattered from recessed defects or damage of a wafer is weaker than the light scattered from projecting foreign particles which are present on a wafer surface. In a case where foreign particles and recessed defects are mixedly present on a wafer, even when an attempt is made to measure only recessed defects, both foreign particles and recessed defects are measured. Thus, sharp, distinctive indication of only recessed defects is infeasible.
The present invention has been conceived to solve the drawback of the background art as described above and is aimed at providing a semiconductor inspection system which can sharply distinguish recesses from foreign particles on a wafer and measure the distribution of recessed defects, such as crystal imperfections or damages, over a wafer while the size and position of desired defects are specified. Further, the present invention is aimed at providing a semiconductor device manufacturing method including an inspection step of inspecting defects of a semiconductor wafer through use of the foregoing semiconductor inspection system.
According to one aspect of the present invention, a semiconductor device inspection system comprises a laser beam radiation section, a detection section and a control section. The laser beam radiation section radiates a laser beam onto a semiconductor wafer to be measured. The detection section detects light scattered from foreign particles or recessed defects formed in the semiconductor wafer, as a result of a laser beam being radiated onto the semiconductor wafer, and converts the detected scattered light into an electric signal. Further, the control section processes the electric signal in the form of data, and outputs information about the recessed defects formed in the semiconductor wafer, by means of subtracting the data pertaining to only the foreign particles located on the semiconductor wafer from the data pertaining to both the foreign particles and recessed defects formed in the semiconductor wafer.
According to another aspect of the present invention, a semiconductor device inspection system comprises a laser beam radiation section, a detection section and a control section. The laser beam radiation section radiates a laser beam onto a semiconductor wafer to be measured. The laser beam radiation section can radiate a laser beam onto the primary surface of the semiconductor wafer by selection of either a normal direction or an oblique direction. The detection section detects light scattered from foreign particles or recessed defects formed in the semiconductor wafer as a result of a laser beam being radiated onto the semiconductor wafer and converts the detected scattered light into an electric signal. The control section processes the electric signal in the form of data, and outputs information about the recessed defects formed in the semiconductor wafer, by means of subtracting the data pertaining to only the foreign particles located on the semiconductor wafer from the data pertaining to both the foreign particles and recessed defects formed in the semiconductor wafer.
According to still another aspect of the present invention, in a method of manufacturing a semiconductor device, a laser beam is radiated onto a semiconductor wafer to be measured. Light scattered from foreign particles or recessed defects formed in the semiconductor wafer is detected, and the detected scattered light is converted into an electric signal. The electric signal is processed in the form of data, and outputted is information about the recessed defects formed in the semiconductor wafer by means of subtracting the data pertaining to only the foreign particles located on the semiconductor wafer from the data pertaining to both the foreign particles and recessed defects formed in the semiconductor wafer.
According to further aspect of the present invention, in a method of manufacturing a semiconductor device, a laser beam is radiated onto a semiconductor wafer to be measured in a normal direction, and light scattered from foreign particles or recessed defects formed in the semiconductor wafer is detected. The detected scattered light is converted into an electric signal, to thereby prepare data pertaining to both foreign particles and recessed defects formed in the semiconductor wafer. Further, a laser beam is radiated onto the primary surface of the semiconductor wafer in an oblique direction, and the light scattered from foreign particles located on the semiconductor wafer is detected. The detected scattered light is converted into an electric signal, to thereby prepare data pertaining to solely foreign particles located on the semiconductor wafer. Then, outputted is information about the recessed defects formed in the semiconductor wafer by means of subtracting the data pertaining to only the foreign particles located on the semiconductor wafer from the data pertaining to both the foreign particles and recessed defects formed in the semiconductor wafer.
Other and further objects, features and advantages of the invention will appear more fully from the following description.